Optical pyrometry



E. A. KEELER.

OPTICAL PYHOMETRY.

APPLICATION HLED 00130, 1919.

41,379,188. mama May mi.

Cri

EARL A.. KEELER, OF NORRISTO'WN, PENNSYLVANIA; ASSIGNOR T0 LEEDS @cNORTH.. RUP COMPANY, F PHLADELPHIA, PENNSYLVANIA, A CORPORATION QFPENN..

SYLVANIA.

or'rIcA-r, PYROMETY.

essaies.

Specification of Letters Patent.

Application filed October 30, 1919. Serial No. 334,496.

To @ZZ f2.0 7mm. it may concern Be it known that LEARL A. Knntnn, acitizen of the United States, residing in Norristown, count-y ofMontgomeiy, State of Pennsylvania, have invented certain new and usefulImprovements in Uptical yrometry, of which the `following is aspeciication.

My invention relates to optical pyrometry Wherein an electric currentpassed through an incandescible body, as an incandescent electric lamp,serving as a light standard, is varied until the brightness of thestandard matches the brightness of the incandescent body whosetemperature is to be measured, the temperature being then determinedfrom the readingr el. a galvanometer whose dcfiection is dependent uponthe amount or current traversing the lamp lilament.

lll/here deiiecting galvanometcrs7 as ot the DArsonval type, areenuriloyed the lower part ol,3 the deflection range of the instrument isuseless because the pyrometer is useless for all tempe atures belowvthat corre- SpOndingWith dull red ot the/lamp filament, because aconsiderable current is required to bring the lamp iilament to dull red,and that current causes substantial deiiection ot' the instrument.

It is the object of my 'invention to -provide a method of and apparatustor optical pyrometry wherein the zero of the instrument is suppressedelectrically in such Way that the lowest part of the range of deflectionof the instrument becomes available, whereby the scale of `theinstrument is lengthened in the sense that it is completely utilized,the lowest teniiperature reading corresponding with the true Zero4 ot'the galvanometer. l

My invention resides in the method and apparat-us hereinafter describedand claimed.

For an illustration ci some of the modes for practising my method and ofsome of the forms my apparatus may take, reference is to be had to theaccompanying drawing. in which:

Figure 1 is av cross sectional view of pyrometric apparatus.

Fig. 2 is a diagrammatic View showing my preferred circuit ar angementsFig. 3 is a diagrammatic view illustrating modified circuitarrangements.

Fig. 4 is an illustration of a scale made available. by my invention..

Referring to Figs. 1 and 2. l is a tube upon which is slidable, the tube2 having at its front end the objective lens 8.- The tube .1 is closedat its rear end -by the member asupporting the eye piece structurehaving the ocular lens 5 1n front of which may be disposed glassscreens, as r and g, of

any suitable colors, as for example, red 0r green. Suitably disposedwithin the tube l is the incandescent lamp L having the lila,- rnent F.Between the lamp L and the objective 3 may be disposed the member ordiaphragm G having the aperture 7 in the 0ptical axis of the instrument.The aperture 8 1s alsoin the axis of the eye piece structure, and theobjective 3. Upon` the member 6 is pivoted at 9 the lever 10 having ahandle l1 extending to the exterior of the telescope structure. lever 10carries the holder 12 in which may be disposed absorption screenelements of any suitable character, as land 14.

With apparatus of the character described in connection With Fignl maybeemployed electrical apparatus of the character illustrated in Fig. 2. InFig. 2 the lamp filament F is-conriected in series with the battery orsource of current B and the variable resistance or rheostat R.

When the filament F is of tungsten or other positive temperaturecoeflicient, it :is preferred that the galvanometer be employed in acircuit in shunt thereto in avoltmeter relation. In Fig. -2 N and Sindicate the north and south poles, respectivelya `01E a permanentm'affnet system of a DArsonv'al galvanometer Whose pivoted coil C isconnected in series in a circuit in shunt to the filament F. Suitableresistances, as a and b, preferably of zero or negligible temperaturecoeflicient, may be' connected in series in said circuit with the coilC.

As thus far described, the apparatus isoperable as follovvs: y i

The telescope instrument of Fig. 1 .is pointed at the body Whosetemperature is to be measured. Unless the body is incandescent, that is,atleast at a dull red `tem'- perature, the optical pyrometric apparatuswould vbe unsuitable. The body being there- Patented May 24, 1921.

At its inner end the'- m nere is@ fore an incandescent one, the rheostatiii is adjusted until current ot such magnitude passes through thelilament l" that it attains the same brightness as the incandescentbody, balance in brightness beim;r determined by placing' the eye at theeye piece 5 and adjusting the rheostat B until a match is attained. Whenobtained the galranometer pointer' detleets to a position somewhere tothe right of the index mark 15 on the instrument scale 1G, Fig'. L1. Theindex Amark 15 corresponds with the dehlection ot the `onlyanometer forthe lowest temperature, as `1200 degrees 11"., at which the opticalinstrument is employed. In accordance with prior practice the entirelower range of the instrument, as 1200 to 23500 degrees F., lies betweenthe index mark 15 and the right end of the scale 16. in' other words,the pointer of the galranometcr dellects from the true Zero index 1T tothe point 1 5 beiiore the lamp filament attains suitable temperature tobe utilizable in optical pyrometry. the index 1i corresponding with they position of the lgalVanometer needle when zero current tlows throughits coil.

By my invention, however, l am enabled to utilize the entire length ofthe scale l@ by utilizing` not only that portion. heretofore utilizable,but also that part lying between the indices '1T and 15, and so inei'iect lengthening' thescale or suppressing the Zero whereby the lowesttemperature, as 'for example 120() degrees, corresponds. with the truezero of the instrument.

This is accrnuplished by connecting in shunt to the galvanorneter coil Cor in shunt to it and any suitable resistance in circuit therewith, asfor example, its usual resistance b, a :aero suppressing or auxiliaryshuntlcircuit, controlledby switch o, including' the source of currentor battery B1, so connected :is to oppose battery B in its effect uponthe galyanometer coil, the adjustable resistance or rheostat R1 and anadditional resistance, as c. The resistances R and `c preferably havezero or negligible temperature coellicients.

With a given ,aalvanometer G and lamp filament F the index mark 15 isdetermined by sighting the instrument upon any incandescent body at` aknown temperature, as for example, 1200 degrees F. The rheostat B isthen adjusted untilsueh currentflows throughfthe filament F as to inducea brightnessA matchingthebrightness of the body atthe'known'temperature. The deection of --the 'Ygal'vanometer is 'thennoted andtheundexmark "15 placed upon the scale .directly:v opposite ithe instrument needleior pointer.l The index 15 therefore correspondswith .1200 degrees or any other predetermined orv suitable knowntempera- `ture constituting the minimum It,emgerature for which' theapparatus is to be utilized.

The switch d is then elosedand the resistance` lil so adjusted that,with the same adjustment of the rheostat R and the same current throughthe filament F as before, the current through the galvanomcter coil C isreduced to Zero, because ot' the effect of the shunt circuit includingthe source B1 now equal and opposite to the etfect produced upon thegalvanometer circuit bythe difference or potential across the terminalsot the lilament I". The galvanometer needle will now point at the index1.7, the true zero ot' the instrument. ll'iith no current flowingthrough the coil C the filament F is at a temperature ot 1200 degreesand in eil'ect the nero or' the instrument has been suppressed in suchmanner that the temperature at the beginning of the useful range of theappa 'atus is now indicated when the galvanometcr needle points its truezero, li'. lil'rith such setting of the resistance R1 he scale 1G maynow he calibrated by matching' the filament l? with differentadjustments ot the rheostat li. upon anincandeseentbody at diiilerentknown temperatures, whereby the scale range, as from 1200 to 2500degrees, will now occupy the entire length oi the scale 16 from theindex 17 to the extreme right.

This in effect lengthens the scale., makes it more easily readable, andall errors, at least for the range below 1200`degrees, as'temperature.magnetic and mechanical errors, and additive errors, are eliminated,particularly since at the beginning of the use- 'ful range of theinstrument no current is flowingr through it; and for errors fortemperature readings above i 1200 degrees F.'

justing the rheostat R until the filament F matches in brightness anincandescent body at known temperature, aslQOO degrees. vlf theLc'alvanometer needle then points at the index 15, it is known that theinstrument stili in perfect calibration.

The auxiliary or Zero suppressing or offsetting circuit preferablyresistance which is high as compared with the resistance oi thegalvanometer circuit, whereby variations of resistance of the auxiliaryeircuit or a variation of voltage of itsbattery B1 shall not materiallyaiect the ratio of the current in thegalvanometer circuit to the currentin the auxiliary circuit.

lilhile the galvanometer Gr of Fig. 2 is employed as a Voltmeter in thesense that the dedection of the coil C depends upon the difference ofpotential between the terminals of the filament F, it may also beemployed in the relation of an ammeter.

In Fig. 3 the gaivanometer G is employed in the aminetcr relation, theterminals of the ammeter seing at 18 and 19, the

terminals ont a resistoneiy e which is of the ammeter instrument, undpreferably o'l' zero or uegligibie temperature coeiiicient. When theainmeter instrument isoonnocte in series with the filament it, theresistente is brought into series with the lihuneut, rheostat il andbttery ln shunt to the resistance und Within the instrument is a circuitincluding; the gul funonieter coil C :uid the resistsnces f' and g,preferably of zero or negligible temperature coeilicients. In shunt tothe coil C and resistance g muy be applied the iuixilisry or v'erosuppress-- in@ circuit as in Fig. 52.

Vith the ammeter arrangement ot F the useful range ot' the instrument,Whe zerov suppressing circuit is absent, is even shorter than indicatedin Fig. 4l for the voltlneterrelation. However, s scale similer t0 thatin Fig. with un index rnarlr, as 15, employed und the Zero is suppressed to the true Zero the instrinnent by closing the switch u? andadjusting the rheostat R1 is above described.

If the instrunfient is to have :i double range, that is, a second rangefor tempera-- tures of say, 2200 degrees und upward the handle 1l isshifted to bring the sorption screens 13, Ul into optical of the.apparatus shown in in. i, und Second series of graduations will then bmede upon the scale l5.

My invention Wiil be understood to be sppiicable to iainp filaments ofpositive torn-- peinture coeiiicient, es of tungsten, etc., and also tofilaments of negative tempereti'ufe coefiicient, as of carbon. y

What l claim is:

l. The method of measuring' teinperuture, Which consists in passingcurrent through an incandescent body, varying said current to bring seidbody to a predetermined 'temperuture, subjecting e gslvunoineter to theeffects ot seid 'current tof produce u dei'iee tion, reducing thepotential difference iu pressed upon galvunoineter r.'

sind maintaining seid current, and theres, tu varyingr the currentthrough said body to bring` it to u brightness to inutch the brimht"ness ot the body Whose temperature to be measured, and determiningtheteniperu-V ture from the resultant deflection of the gulvanometer.

2. The method. ot measuring; temperature, which consists in passino;current through :in incandescent body. varying; said current to bring);said body to :i predetermined teniperature, subjectinga. galvzinorneterto the effects of seid current to produce u. deflec-v tion, reducing thedeflection of said gelminometer by impressing thereon fx1 opposingelectr0-motivetorse, and thereafter Viry@ ing the current through seidbody to bring it to s brightness to match the-brightness of the bodyWhose temperature is to be "er, and deterroiniirgP the temperature eresultant deflection of 'the gnihed oif rnausuring temperature, "on isin passing ourrent through 'endeseent body7 turying seid current nogsaid body to :i predeterlnined teinure, subjecting` s gelvsnonieter tothe ettects of said current to produce il, deflection, reducing' thedeflection of the gulvanoineter en in to l `to sceroby impr ssingthereon en opposing;`

u. neue fruireuoinetor ooperuting with on e incuruleseed light standardin roinelry, which Consists in oppos oenotiye--if l impressed ,A by thecurrent trui'- u. predetermined tein- ,sconce un equal and oproree,whereby the det vzinometer ris zero for seid pred finpersture.

The method of prod using' a seele tor u gzilvenorueter coo "eroting'with an electricu :undefined iody optical l'yronietry, 'which consistsin opposing' to the electroinotiwaioroe impressed upon said gslvanonb bythe current traversing said light standard et u. predeterminedtemperature uit' incandesccnce un equal und opposite elec`Vtro'iwtivo-torce, vwhereby the deflection of saidV golyunoineter is zero.tor seid predeter ruined temperature, thereafter bringing saidinczuidesced light standard to higher predetei 'uned temperatura endmarking said scuole in correspondence with the deiiections of saidgslvsnornoter seid temperstores.

7, Uptionl 'oyron'ietric :ipp ing un inoi -u .nt body, e. source ofcurrent therefor, meer 'for varying the strength of the efirront throughseid body, e. gelvsnorneter Whose deileotion depends upon the stratuscom prisstrengrth ot the current through satidbody,v

eter Whose deiiection depends upon the corresponding -with isotheicurrent through said body,

. tion oi the galvanorneter, and a scale for `strength of the currentsaid galvanonieter calibrated in temperature units and having lfor zerodeflection a read* ing corres ,wending 'with a temperature ot Visibleincandescence.

l0. @ptical pyroinetric apparatus corre prising an incandescent body, asource of current there-tor, means for vznying the strength ot thecurrent through said body, a galvanorneter whose deliection depends uponthe strength ot the current Athroagh said body, a zero suppressing shuntcircuit coin,- prising a resistance and a source o" current connected inopposition to said first narned soared-'and a scale t'or saidgalvanoincter calibrated in temperature units and haring for Zerodeflection of said galyanoincter a reading corresponding with atemperature of visible incandescence.

l1. Optical p yroinetric apparatus comprise ing an incandescentbody, asource ot current therefor, means for Varying the strength ot thecurrent through said body, a galvanometer in a shunt to said body, andan auxiliary circuit comprising a source of current `and a variableresistance for changing the deflection of the galvanorneter.

l2. Optical pyrornetric apparatus coinprising an incandescent body, asource ot" current therefor, means for varying the through said body, agalvanorncter in a shunt to said body, and a Zero suppressing circuit ina shunt relation with respect to said galyanoineter compris: ing avariable resistance and a source of current connected infr oppositionto' said. irst named source.

v13. Optical -pyrornetric apparatus coniprising an incandescent body, asource of current therefor, means for varying the strength of thecurrent through said body, a galvanoineter in a shunt to said body, anauxiliary circuitcomprising a source oil current and a resistance forchanging the dciiection of the galvanoniet and auscale tor saidgalvanonieter calibrated in temperature units and having for zerodeflection of said galvanorneter a reading correspomling with atemperature ot visible incandescenne.

14%. Optical pyroinetric apparatus coniprising an incandescent body, asource of" current therefor, means for varying the strength of thecurrent through said body, a galvanoineter in a shunt to said body, azero suppressing circuit in a'shunt relation With p said galvanonietercomprising a variable refprising a standard lamp having an I'incanl,

(flescing ilaroent, a source ot' current and Variable resistancein'circuit with said filament, a galvanonieter Whose dciiection dependsupon the strength et current through said filament, and an auxiliarycircuit comprising resistance and a source of current connected inopposition to said lirst named source of' current.

le. ptical pyronietric apparatus' coniprising standard lamp having anincan- Ydcscing lilainent of positive temperature covariable lresistance 1n cncult therewith, a galvanoetlicient, a source of currentand nieter connected .in a shunt to said ilament, a circuit connected ina Ishunt relation with said galvanonieter comprising a resistance andsource of current connected in opposition to said first named source.

li'. Optical pyrornetric apparatus comprising a'standard lamp having anincaud est ng Filament, a source of current and variable resistance incircuit with said filament, galranoineter Whose deflection depends uponthcstrength of current through said filament, an auxiliary circuitcomprising a source of current connected in opposition to said firstnamed source ot' current and a resistance, and a scale for saidgalvauorneter calibrated in temperature units and having for zerodeflection a reading corresponding with a temperature ofvisible'incandescence.

itt ptical pyroinetric apparatus cornprising a standard lamp havinganincandescing filament ott positive temperature coetilcient, source ofcurrent and `variable resistance in circuit therewith, a galvanorneterconnectedin a shunt to said filament, a circuit connected in shuntrelation with :aid

'alvanonieter coni i risino a source of current-- 1 b connected inopposition to said lirst named source and a resistance, and a scale forsaid galvanonieter calibrated in temperature units and having for Zerodeflection oi said galyanonieter a reading corresponding with atenuierature of Visible incandesccnce.

Vln testimony Whereot` l have hereunto alined my signature this Qtlrdayof 0ctober, 1919. i

EARL A.. KEELER.

